An open reading frame in the Escherichia coli bacteriophage lambda genome encodes a protein that functions in assembly of the long tail fibers of bacteriophage T4.

Assembly of the long tail fibers of the Escherichia coli bacteriophage T4 requires the catalytic action of two auxiliary proteins. It was found that a gene of the entirely unrelated phage lambda codes for a protein which can substitute for one of these T4 polypeptides, protein 38. The lambda gene was designated tfa (tail fiber assembly). Protein 38 consists of 183 residues, and the Tfa protein consists of 194 residues; the two polypeptides are about 40% homologous. Although the tfa gene is dispensable for the growth of phage lambda, these results indicate that it may have a function in lambda morphogenesis.